The polymeric immunoglobulin receptor (secretory component) in a human intestinal epithelial cell line is up‐regulated by interleukin‐1

Secretory component (SC or polymeric immunoglobulin receptor) on mucosal epithelial cells mediates transcytosis of polymeric immunoglobulin into external fluids and functions as a receptor for polymeric immunoglobulin. SC expression in a human colonic adenocarcinoma cell line, HT‐29 has been reported to be up‐regulated by various cytokines, such as interferon‐ , tumour necrosis factor‐ and interleukin‐4 (IL‐4). However, up‐regulation of SC by IL‐1 is controversial. In this study, we investigated the effect of human recombinant IL‐1 alone on SC expression in HT‐29 cells in detail. Immunocytochemistry and Northern blot analysis revealed that IL‐1 increased both the number of SC‐positive cells and SC mRNA expression. Enzyme‐linked immunosorbent assay revealed that IL‐1 enhanced secretion by HT‐29 cells in both time‐ and dose‐dependent manners. IL‐1 had the same effects on HT‐29 cells. Northern blot analysis demonstrated that cycloheximide and actinomycin D abolished the effect of IL‐1. Moreover, we detected IL‐1 receptor (IL‐1R) type I mRNA in HT‐29 cells by polymerase chain reaction (PCR) and sequenced the PCR‐amplified product. We think that it reflects the possibility of the presence of IL‐1R in HT‐29 cells. From these data, we concluded that IL‐1 and IL‐1 play regulatory roles in SC expression, and their effects depend on de novo protein synthesis and transcription.